Powering a Redstone Lamp on top of a Piston

In the latest snapshot of 1.8, this has become really easy. Here's a view of the redstone (the piston is sticky):

Those furnaces have to be something that can not be pushed by a piston, a furnace is the cheapest, but you can also use obsidian.

Top view:

Everything covered up:

EDIT: nightcracker has provided a much simpler answer, so this answer is only valid if you don't use Slime blocks for religious reasons :-)

EDIT 2: even if so, go use Bergi's design, it is still superior :-)

This is possible, albeit complex.

My prototype has 1 regular and 6 sticky pistons, and 6 redstone inputs that need to be cycled in a correct order for it to work. I'm afraid to think of control circuits it will require (either under each lamp, or 6 wires from the center to each lamp).

I am not very experienced in optimizing redstone signals, so I have limited myself to the mechanical part. If you finish this, please share!

Here's the simplest way, although it does have a single piece of redstone + a couple half slabs:

Day

Night

Covered up

The concept behind it is hooking the sticky piston and the anticipated position of the raised lamp up to a NOT gate, so when the sun goes down, the lack of power triggers both the piston and subsequently powers the lamp.